The airspace above the modern battlespace is becoming increasingly congested, making effective coordination, integration, and deconfliction by friendly forces a growing challenge. This modern airspace clutter is now being exacerbated by the combined use of manned and unmanned aerial vehicles operating in close proximity to each other. Unmanned aerial vehicles pose significant challenges to airspace deconfliction due to their agility, small size, and increasing density in the airspace. The unmanned aerial vehicles create a potential friendly-aircraft-collision hazard in military airspace. The number of unmanned aerial vehicles in commercial airspaces is expected to increase so that unmanned aerial vehicles are expected to create a potential friendly-aircraft-collision hazard in commercial airspace.
Identifying air assets in the combat zone and the lower-altitude terrain flight environment is difficult and depends on a mix of procedural (area situation awareness) and positive (spot) control measures. The primary positive means of identification are: 1) visual; 2) military identification friend or foe (IFF) systems; and 3) commercial selective identification features (SIF) systems. Currently, unmanned aerial vehicles have limited ability to detect and avoid other aircraft, are unable to identify their position, and cannot confirm friendly status. Unmanned aerial vehicle avoidance is thus limited to mainly visual detection, which poses an operational hazard and distraction to manned aircraft operating nearby. The development and/or deployment of a feasible solution to locate/identify small unmanned aerial vehicle positions in military airspace has been limited by issues related to cost, size, impact to existing IFF/SIF system, and installation logistics. The same issues have limited the use of unescorted unmanned aerial vehicles in National Airspace System (NAS), the aviation system that enables safe air travel in the United States and over large portions of the world's oceans.